Radio communication system, base station apparatus, user terminal and radio communication method

ABSTRACT

The present invention is designed to make it possible to apply power scaling to a period where the upper limit value is exceeded, while maintaining uplink transmission quality. In a radio communication system  1  in which multiple cells (C 1  and C 2 ) are formed, a base station apparatus ( 20 ) forms a first cell C 1 , which is one of the multiple cells, and has a control section ( 234 ) that controls uplink transmission times per timing group, which includes one component carrier or a plurality of component carriers, and a transmission section ( 106 ) that signals a timing group or a component carrier determined as a target of power scaling, as power scaling target information, in which the timing group or the component carrier, to which power scaling is applied, is expressly determined, to a the user terminal ( 10 ).

TECHNICAL FIELD

The present invention relates to a radio communication system, a basestation apparatus, a user terminal and a radio communication method tocarry out multi-carrier transmission with a plurality of connectingcells at different times on the uplink.

BACKGROUND ART

LTE (Long Term Evolution) has been under study heretofore, for thepurposes of achieving improved spectral efficiency and peak data rates,reducing delays and so on in UMTS (Universal Mobile TelecommunicationsSystem) (non-patent literature 1). As a result of this, in Release-8 LTE(hereinafter referred to as “Rel. 8-LTE”), as radio access schemes, ascheme that is based on orthogonal frequency division multiplexingaccess (OFDMA) was employed for the downlink, and a scheme that is basedon single-carrier frequency division multiple access (SC-FDMA) wasemployed for the uplink. In Rel. 8-LTE, it is possible to achievetransmission rates of approximately maximum 300 Mbps on the downlink and75 Mbps on the uplink, by using a variable band that ranges from 1.4 MHzto 20 MHz. Presently, in 3GPP, successor systems of LTE (referred to as“LTE advanced” (“LTE-A”)) are under study for the purpose of achievingfurther broadbandization and faster speed beyond the UMTS network.

Recently, a study is progress to achieve increased network capacity bybuilding a heterogeneous network (HetNet), in which low-power nodes(LPN) of low transmission power are overlaid in the area of a macrocell, and applying carrier aggregation (CA) to the HetNet. Carrieraggregation refers to the technique of achieving broadbandization byusing a frequency band (1.4 MHz to 20 MHz) that is supported in LTE asone component carrier (CC) and using multiple CCs at the same time. Inthe HetNet, it is possible to realize efficient user terminal control,traffic off-loading and so on, by changing the connecting cell to whicha user terminal is connected, on a per CC basis.

FIG. 1 shows, as an example, a state in which a user terminal UE isconnected with two cells of a base station apparatus eNB (macro cell)and a low power node LPN (low power cell) in a HetNet. The user terminalUE is allocated component carriers CC #1 and CC #2 by carrieraggregation, and connects with the macro cell via component carrier CC#1 and connects with the low power cell via component carrier CC #2.Since the low power node LPN 2 has a small cell, the user terminal UE islocated in a position closer to the low power node LPN than to the basestation apparatus eNB. In Rel. 11-LTE, which is the latest standard ofLTE-A, an MTA (Multiple Timing Advance) function to make it possible todefine a plurality of transmission times for a plurality of CCs on theuplink is introduced (up to Rel. 10, a user terminal is subject tosingle-transmission time control (which is referred to as “TA” or“single TA”)), for the purpose of coordinating the times of receptionbetween separate nodes (base station apparatus, low power node and soon). In the example shown in FIG. 1, the macro cell carries out uplinktransmission at a transmission time T1, and the low power cell carriesout uplink transmission at a transmission time T2, which is apredetermined time delayed from transmission time T1.

In LTE-A, carrier aggregation to use maximum five CCs is realized. InMTA, which is introduced in Rel. 11-LTE, maximum five CC are classifiedinto maximum four TA groups (TAGs), and the times of transmission arecontrolled on a per TAG basis.

As an example, FIG. 2 shows a state in which five CCs are classifiedinto four TAGs. Five of CC #1 to CC #5 are classified into four of TAG#1 to TAG #4. TAG #1 is assigned to CC #1, one TAG #2 is assigned to twoof CC #2 and CC #3, TAG #3 is assigned to CC #4, and TAG #4 is assignedto CC #5.

When the times of uplink transmission are controlled on a per TAG basisin a user terminal UE where MTA is applied, as shown in FIG. 3, thedifference between the transmission times of the TAGs may develop toapproximately 30 μs at a maximum. FIG. 3 shows a state in which thetransmission times of TAG #1 and TAG #2 are, for example, 30 μsdifferent.

CITATION LIST Non-Patent Literature

-   Non-Patent Literature 1: 3GPP, TR25.912 (V7.1.0), “Feasibility Study    for Evolved UTRA and UTRAN,” September 2006-   Non-Patent Literature 2: 3GPP, TS36.211 Sec. 8.1, “Timing Advance”

SUMMARY OF THE INVENTION Technical Problem

In the uplink in the LTE-A system, transmission power is controlled inCC units and in subframe units, and is controlled so that the totaltransmission power in each subframe does not exceed an upper limit.

When the MTA function introduced in Rel. 11-LTE is applied to a userterminal, there is a concern that parts (PO: Partial Overlap) wheresubframes overlap between TAGs may be produced, and there is also apossibility that the upper limit of transmission power is exceeded inthe PO periods. For example, even if, as shown in FIG. 4, transmissionpower is controlled in subframe units, on a per TAG basis, such that,when one TAG enters a high power subframe period, the other TAG enters alow power subframe period, if a PO period in which high power subframesoverlap between the TAGs is produced, the upper limit of transmissionpower is exceeded in the PO period. So, when there is a possibility thatthe total transmission power in a PO period exceeds the upper limit, itis necessary to apply power scaling to the PO period or to the entiresubframe period, and reduce the total transmission power. When “powerscaling” is mentioned herein, this refers not only to reducing power,but also covers cases where power is made zero.

However, when power scaling is applied to a PO period, signal powerdecreases, and therefore a problem arises that uplink transmissionquality is deteriorated.

The present invention has been made in view of the above, and it istherefore an object of the present invention to provide a radiocommunication system, a user terminal, a base station apparatus and aradio communication method whereby it is possible to apply power scalingto PO periods while maintaining uplink transmission quality.

Solution to Problem

The radio communication system according to the present invention is aradio communication system, in which multiple cells are formed, andwhich has a plurality of base station apparatuses that each form a cellincluded in the multiple cells, and a user terminal that can connect toat least a first cell and a second cell included in the multiple cells,and, in this radio communication system, the base station apparatuseshas a control section that controls uplink transmission times per timinggroup including one component carrier or a plurality of componentcarriers, and a transmission section that signals a timing group or acomponent carrier determined as a target of power scaling, as powerscaling target information, in which the timing group or the componentcarrier, to which power scaling is applied, is expressly determined, tothe user terminal, and the user terminal has a receiving section thatreceives the power scaling target information signaled from the basestation apparatus, a transmission section that transmits uplink signalsat different transmission times per timing group, and a power controlsection that, when a total of uplink signal transmission power over thefirst cell and the second cell exceeds a predetermined value, appliespower scaling to the timing group or the component carrier determined inthe power scaling target information.

The base station apparatus according to the present invention is a basestation apparatus that forms a cell in a radio communication systemwhere multiple cells are formed, and this base station apparatus has acontrol section that controls uplink transmission times per timing groupincluding one component carrier or a plurality of component carriers,and a transmission section that signals a timing group or a componentcarrier determined as a target of power scaling, as power scaling targetinformation, in which the timing group or the component carrier, towhich power scaling is applied, is expressly determined, to the a userterminal, and the user terminal is connected to multiple cells andcontrolled to different transmission times per timing group.

The user terminal according to the present invention is a user terminalthat connects to multiple cells in a radio communication system where aplurality of base station apparatuses form multiple cells, and this userterminal has a receiving section that receives power scaling targetinformation signaled from a base station apparatus, a transmissionsection that transmits uplink signals at different transmission timesper timing group, and a power control section that, when a total ofuplink signal transmission power over connecting cells exceeds apredetermined value, applies power scaling to the timing group or thecomponent carrier determined in the power scaling target information.

The radio communication method according to the present invention is aradio communication method in a radio communication system wheremultiple cells are formed, and the radio communication system has aplurality of base station apparatuses that each form a cell included inthe multiple cells, and a user terminal that can connect to at least afirst cell and a second cell included in the multiple cells, and theradio communication method includes the steps of controlling uplinktransmission times per timing group including one component carrier or aplurality of component carriers, signaling a timing group or a componentcarrier determined as a target of power scaling, as power scaling targetinformation, in which the timing group or the component carrier, towhich power scaling is applied, is expressly determined, to the userterminal, in the user terminal, receiving the power scaling targetinformation signaled from the base station apparatus, transmittinguplink signals at different transmission times per timing group, and,when a total of uplink signal transmission power over multiple cells, towhich the user terminal is connected at the same time, exceeds apredetermined value, applying power scaling to the timing group or thecomponent carrier determined in the power scaling target information.

Technical Advantage of the Invention

According to the present invention, it is possible to apply powerscaling to periods in which uplink transmission power exceeds an upperlimit value, while maintaining uplink transmission quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram to explain a HetNet;

FIG. 2 is a diagram to show the relationship between component carriersand TAGs;

FIG. 3 is a diagram to show a state in which the time of transmission isdifferent between TAGs;

FIG. 4 is a diagram to show a PO period in which high power subframesoverlap between TAGs;

FIG. 5 is a diagram to explain an example of application of powerscaling;

FIG. 6 is a diagram to explain a system structure of a radiocommunication system according to an embodiment;

FIG. 7 is a block diagram to show a schematic configuration of a basestation apparatus according to an embodiment;

FIG. 8 is a block diagram to show a configuration of a baseband signalprocessing section in a base station apparatus;

FIG. 9 is a block diagram to show a schematic configuration of a mobileterminal apparatus according to an embodiment;

FIG. 10 is a block diagram to show a configuration of a baseband signalprocessing section in a mobile station apparatus; and

FIG. 11 is a block diagram to show a configuration of a layer 1processing section in a baseband signal processing section of a mobilestation apparatus.

DESCRIPTION OF EMBODIMENTS

A gist of the present invention is that a base station apparatus eNBexpressly determines a TAG (or a cell, a CC, an uplink physical channel,etc.), to which a user terminal UE should apply power scalingpreferentially, and signals power scaling target information forspecifying the TAG and/or the like, to which power scaling is to beapplied preferentially, to the user terminal UE. By this means, it ispossible to determine the TAG and/or the like, to which the userterminal UE should apply power scaling, in the base station apparatuseNB, so that it is possible to improve the flexibility in networkmanagement. The base station apparatus eNB can flexibly determine theTAG (or cell, CC, uplink physical channel, etc.) to apply power scalingto, such that the deterioration of uplink transmission quality isreduced, by taking into account the communication environment (cellconfigurations, the conditions of carrier aggregation, transmissionquality, traffic, transmission power, transport block size, and so on).

Now, the details will be described with reference to the networkconfiguration shown in FIG. 1. A user terminal UE is connected with amacro cell (base station apparatus eNB), which serves as a first cell,and is also connected with a low power cell (low power node LPN), whichserves as a second cell. It is not an essential requirement of thepresent invention that the first cell should be a macro cell and thesecond cell should be a low power cell. The present invention by nomeans limits the number of cells to which a user terminal can beconnected at the same time to two cells. The base station apparatus eNBand the low power node LPN are connected via a backhaul link, and thebase station apparatus eNB controls the low power node LPN. The lowpower node LPN receives information (for example, TAG information) thatis required for communication with user terminals UE from the basestation apparatus eNB via the backhaul link.

The base station apparatus eNB allocates a plurality of componentcarriers CC #1 and CC #2 to the user terminal UE by carrier aggregation,and also commands the cell configurations to the user terminal UE sothat one component carrier CC #1 is allocated to the macro cell and theother component carrier CC #2 is allocated to the low power cell. Whenthe cells are configured such that the user terminal UE is assigned aplurality of component carriers and is connected with a plurality ofcells at the same time, the base station apparatus eNB classifies theplurality of component carriers assigned to the user terminal UE intoTAGs, and controls the times of transmission on a per TAG basis. In theexample shown in FIG. 1, CC #1 that is allocated to the macro cell isclassified as TAG #1, and CC #2 that is allocated to the low power cellis classified as TAG #2.

The user terminal UE can transmit an uplink physical control channel andan uplink physical data channel via a plurality of component carriers CC#1 and CC #2. To be more specific, the user terminal UE controls thetime to transmit uplink subframes to transmission time T1 incommunication with the macro cell (TAG #1 and CC #1), and controls thetime to transmit uplink subframes to transmission time T2 incommunication with the low power cell (TAG #2 and CC #2). At this time,TAG #1 and TAG #2 offer different times for uplink transmission (T1 andT2), and therefore a PO period is produced (see FIG. 4).

The base station apparatus eNB expressly determines the TAG to whichpower scaling is applied in the user terminal UE. For example, in orderto determine the TAG to apply power scaling to, it may be possible touse transmission quality as a basis for decision making. For example,although the deterioration of the transmission quality of TAG #1 (CC #1)might cause severe difficulties in radio communication, a communicationenvironment may be designed, in which the transmission quality of TAG #2(CC #2), even when deteriorated, can be recovered. In this case, thebase station apparatus eNB can determine TAG #2 (CC #2) as the TAG towhich power scaling is applied. Alternatively, it is also possible touse traffic as a basis for decision making in order to determine the TAGto apply power scaling to. For example, assume a case where the trafficin TAG #1 (CC #1) is very low and the traffic in TAG #2 (CC #2) is keptto a high value. In this case, the base station apparatus eNB candetermine TAG #1 (CC #1) as the TAG to which power scaling is applied.By using transmission quality and traffic as basis for decision making,it is possible to apply power scaling to a PO period so that thedeterioration of uplink transmission quality can be reduced.

The base station apparatus eNB can also use the cell configurations as abasis for decision making and expressly determine the TAG where powerscaling is applied in the user terminal UE. Carrier aggregation refersto the kind of communication by multiple cells using a plurality ofcomponent carriers. It is also possible to define multiple cells(component carriers) as two different types of cells by defining onecell as a primary cell (Pcell) and the other cell as a secondary cell(Scell). The base station apparatus eNB independently configures theprimary cell and the secondary cell for the user terminal UE that adoptswhere carrier aggregation. The primary cell is always formed with a set(combination) of one downlink component carrier and one uplink componentcarrier. The secondary cell is formed with at least one downlinkcomponent carrier, and there are cases where an uplink component carrieris incorporated or not incorporated. Here, the secondary cell is alsoformed with an uplink component carrier.

A case will be assumed here where, in the HetNet shown in FIG. 1, theprimary cell (TAG #1 and CC #1) is managed for control signals and thesecondary cell (TAG #2 and CC #2) is managed for data transmission. InRel. 10-LTE, the following uplink physical channel configurations aredefined in component carrier units. As uplink physical channels, aphysical random access channel (PRACH), a physical uplink controlchannel (PUCCH), a physical uplink shared channel (PUSCH), and a channelquality measurement reference signal (SRS: Sounding Reference Signal)are defined. The PRACH is used when the user terminal makes initialaccess to the network. From the downlink component carrier that isdetected in cell search, the user terminal receives, as broadcastinformation that is necessary, the parameters of the PRACH (thefrequency position, the subframe position, the Zadoff-Chu sequence indexand so on), information about the uplink component carrier (the centerfrequency, the bandwidth and so on), and so on, and transmits the PRACHusing the uplink component carrier that correspond to the downlink. ThePUCCH is multiplexed at both ends of the band (intra-subframe frequencyhopping is applied), and carries ACKs/NACKs, which are response signals(responses) to downlink transmission signals, CQI (Channel QualityIndicator) reports, scheduling requests and so on. CQI refers to qualityinformation that shows the quality of data as received, or the qualityof communication channels. The PUSCH is mapped a UL-SCH (an uplinkshared channel, which is one transport channel).

The base station apparatus eNB expressly determines the cell (theprimary cell or the secondary cell) to apply power scaling to, as anexample of using cell configurations as a basis for decision making. Forexample, when the first cell is managed for control signals and thesecond cell is operated for data transmission and the component carriersincluded in the first cell are classified as the first timing group, andthe component carriers included in the second cell are classified as thesecond timing group, the base station apparatus eNB expressly determinesthe physical uplink control channel (PUCCH) of the first timing group,the physical uplink shared channel (PUSCH) of the second timing group,and the reference signal (SRS) for channel quality measurement, asphysical channels to apply power scaling to.

If the primary cell for control signals (TAG #1 and CC #1) becomes thetarget of power scaling, the transmission power for the control signal(PUCCH) in the primary cell (TAG #1 and CC #1) decreases. If thesecondary cell for data transmission (TAG #2 and CC #2) becomes thetarget of power scaling, the transmission power of the data signal(PUSCH) in the secondary cell decreases. Since the cell to which powerscaling is applied (the primary cell or the secondary cell) is reportedto the user terminal UE, it is possible to apply power scaling to thecontrol signal (PUCCH) or the data signal (PUSCH) by signaling in cellunits in the HetNet environment.

The base station apparatus eNB may expressly determine the cell to applypower scaling to, by linking physical channels with the cells, as anexample of using cell configurations as a basis for decision making. Tobe more specific, if the primary cell for control signals (TAG #1 and CC#1) becomes the target of power scaling, the data signal (PUSCH) in theprimary cell may be determined to be subject to power scaling, and,similarly, if the secondary cell for data transmission (TAG #2 and CC#2) becomes the target of power scaling, the control signal (PUCCH) inthe secondary cell is may be determined to be subject to power scaling.By this means, power scaling in physical channel units is made possibleby reporting the cell to apply power scaling to (the primary cell or thesecondary cell), to the user terminal UE.

The base station apparatus eNB expressly determines the physicalchannels to apply power scaling to, in physical channel units. Forexample, in the primary cell (TAG #1 and CC #1), it is assumed that thetransmission quality of the PRACH and the PUCCH is prioritized over thePUSCH, and, in the secondary cell (TAG #2 and CC #2), it is assumed thatthe transmission quality of the PUSCH and the SRS is prioritized overthe PUCCH. In this case, the base station apparatus eNB expresslydetermines the PUSCH of TAG #1 (CC #1) as the target to which applypower scaling is applied, and expressly determines the PUCCH of TAG #2(CC #2) as the target to which power scaling is applied to.

The base station apparatus eNB reports the TAG (or the cell, the CC, theuplink physical channel, etc.) to be the target of power scaling,determined by one of the above-described methods, to the user terminalUE by higher layer signaling. By this means, it is possible to minimizethe overhead, which increases by signaling the TAG (or the cell, the CC,the uplink physical channel, etc.), to which power scaling is applied.

The TAG (or the cell, the CC, the uplink physical channel, the packet,etc.) to apply power scaling to is reported from the base stationapparatus eNB to the user terminal UE through the downlink. In the statein which MTA is applied to the user terminal, if the total transmissionpower exceeds the upper limit, the user terminal UE applies powerscaling to the TAG (or the cell, the CC, the uplink physical channel,etc.) and reduces the transmission power.

Assume that, in the state the user terminal UE is connected to multiplecells, the TAG to apply power scaling to is reported. In this case, ifMTA is applied to the user terminal UE and the total transmission powerexceeds the upper limit in a PO period, the transmission power of the CCthat is included in the TAG reported in advance is reduced.

Assume that, in the state in which the user terminal UE is connected tothe primary cell and the secondary cell, for example, the primary cell(or the secondary cell) is reported as the cell to which power scalingis applied. In this case, if MTA is applied to the user terminal UE andthe total transmission power exceeds the upper limit in a PO period, thetransmission power of the primary cell (or the secondary cell) that isreported in advance is reduced.

The user terminal UE may acquire information that links physicalchannels with cells, in advance, and have the cell where power scalingis applied reported from the base station apparatus eNB. For example,assume that, when the primary cell for control signals (TAG #1 and CC#1) becomes the target of power scaling, the data signal (PUSCH) in theprimary cell is determined to be subject to power scaling. When thetotal transmission power exceeds the upper limit in the PO period, ifthe primary cell (TAG #1 and CC #1) is reported in advance as the targetof power scaling, the user terminal UE reduces the transmission power ofthe PUSCH of the primary cell. Alternatively, assume that, when thesecondary cell for data transmission (TAG #2 and CC #2) becomes thetarget of power scaling, the control signal (PUCCH) in the secondarycell is determined to be subject to power scaling. When the totaltransmission power exceeds the upper limit in the PO period, if thesecondary cell (TAG #2 and CC #2) is reported in advance as the targetof power scaling, the user terminal UE reduces the transmission power ofthe PUCCH of the secondary cell.

When the base station apparatus eNB expressly determines the PUSCH ofTAG #1 (CC #1) as the target to apply power scaling to, and expresslydetermines the PUCCH of TAG #2 (CC #2) as the target to apply powerscaling to, the user terminal UE has information about the targets ofpower scaling determined in this way reported from the base stationapparatus eNB. In this case, when the total transmission power in the POperiod exceeds the upper limit, the user terminal UE reduces thetransmission power of the physical channels that are reported inadvance. For example, if the PUSCH of TAG #1 (CC #1) is determined to bethe target to apply power scaling to, the transmission power of thePUSCH of TAG #1 (CC #1) is reduced.

It is possible to combine the above-method of applying power scalingwith one of methods A and B, which will be shown below.

The power scaling method A applies power scaling on a per physicalchannel basis based on the priority of each uplink physical channel(PUSCH/PUCCH/PRACH/SRS). For example, the priorities are determined suchthat: PRACH>PUCCH>PUSCH>SRS.

The power scaling method B applies power scaling by prioritizing theprimary cell over the secondary cell.

Another aspect of the present invention provides a method of maintainingtransmission quality by implicitly determining the TAG and/or the like,to which power scaling is applied, without signaling. Specific powersignaling methods (1) to (5) will be described below.

(1) The user terminal UE may be configured to apply power scaling to aTAG having large transmission power. By this means, the probability thatpower scaling is applied to a TAG having low transmission powerdecreases, and it is possible to prevent the significant qualitydeterioration due to the severe reduction of power to allocate to theTAG having low transmission power.

Assume a case where, in the state in which the user terminal UE isconnected to multiple cells, MTA to provide a plurality of transmissiontimes for a plurality of connecting cells on the uplink is applied tothe user terminal UE. TAG configurations (the component carrier numbers,information corresponding to the TAG numbers, and so on) related to thecomponent carriers allocated by the base station apparatus eNB isreported to the user terminal UE.

As shown in FIG. 5, a plurality of component carriers, allocated to theuplink of the user terminal UE, are classified to TAG #1 and TAG #2. Astate is shown here where the transmission power of TAG #1 is greaterthan the transmission power of TAG #2 in a stage before power scaling isapplied.

When the total transmission power on the uplink exceeds the upper limitin the PO period, the user terminal UE applies power scaling to TAG #1having the greater transmission power. As a result of this, as shown inFIG. 5, the transmission power of TAG #1 decreases, and the totaltransmission power is reduced to or below the upper limit. At this time,the transmission power of TAG #2, to which power scaling is not applied,is maintained.

(2) The user terminal UE may be configured to apply power scaling to aPUSCH where the transport block size (the number of transmission bits)is small. By this means, the small-sized transport block can preventquality deterioration by means of power scaling, and reduce the overheadupon retransmissions, unlike large-sized transport blocks that causequality deterioration.

In LTE, data on an uplink transport channel (for example, the UL-SCH) isincorporated into transport blocks of certain size. In each subframe(transmission time interval: TTI), transport blocks are transmitted onthe radio interface between the user terminal UE and the base stationapparatus eNB. The transport blocks are divided into codewords andtransmitted by physical channels. In the event of one-antennatransmission, one transport block of variable size is transmitted on perTTI. In the event of multiple-antenna transmission, maximum twotransport blocks of variable size are transmitted per TTI. The transportblock size is defined in the transport format that accompanies thetransport blocks. In the transport format, the modulation scheme andantenna mapping are defined, besides the transport block size.

When the user terminal UE is connected to the first cell and the secondcell and the total transmission power on the uplink exceeds the upperlimit in the PO period, between the transport block allocated to thePUSCH of the first cell and the transport block allocated to the PUSCHof the second cell, the user terminal UE applies power scaling to thePUSCH of the smaller transport block size.

(3) The user terminal UE may be configured to apply power scaling to aTAG where the total allocation bandwidth is small. By this means, it ispossible to reduce the frequency bandwidth to consume.

One component carrier or a plurality of component carriers areclassified into one TAG, so that there is a possibility that the totalallocation bandwidth varies between TAGs. For example, TAG #1 isallocated only one component carrier CC #1, and TAG #2 is allocated twocomponent carriers CC #2 and CC #3.

Assume a case where, in the state in which the user terminal UE isconnected to multiple cells, MTA to provide a plurality of transmissiontimes for a plurality of connecting cells on the uplink is applied tothe user terminal UE. TAG configurations (the component carrier numbers,information corresponding to the TAG numbers, and so on) related to thecomponent carriers allocated by the base station apparatus eNB isreported to the user terminal UE. When the total transmission power onthe uplink exceeds the upper limit in the PO period, the user terminalUE applies power scaling to TAG #1 where the total bandwidth is smaller.

(4) The user terminal UE may be configured to apply power scaling to newuplink packets. By this means, although there is a possibility that,when the transmission power of uplink retransmission packets is reduced,reception errors occur again and the delays accumulate, since thetransmission power of new packets is reduced, it is possible to minimizethe delay time even if retransmissions occur.

As noted earlier, in each uplink component carrier, uplink channels suchas the PUCCH, the PUSCH and so on are placed. The user terminal UEtransmits channel state information (CSI) that represents downlinkchannel states, information that represents ACKs/NACKs (positiveacknowledgement/negative acknowledgement) in hybrid ARQ in response todownlink transport blocks, uplink control information (UCI) such asscheduling requests (SRs), to the base station apparatus eNB, by usingthe PUCCH and/or the PUSCH.

In LTE, retransmissions of damaged/lost data or data that has errors arefirst processed in MAC layer hybrid ARQ, and, if recovery fails even bythis processing, handled in the RLC retransmission protocol. Hybrid ARQis designed for the purpose of allowing quick retransmissions, so thatdecoding process results are fed back in response to every transmission.The base station apparatus eNB and the user terminal UE each have ahybrid ARQ entity, and each hybrid ARQ entity is comprised of the hybridARQ process. On the receiving side, when a transport block intended forthe hybrid ARQ process is received, decoding of the block is tried, andthe result—that is, whether or not the block has been receivedcorrectly—is reported to the transmitting side by way of an ACK/NACK.

On the uplink, which subframes are retransmitted is always known. In theevent of FDD, a retransmission is carried out eight subframes after adata transmission is tried. Whether or not retransmission should becarried out on the uplink is controlled based on new data indicators(NDIs) included in scheduling grants for the uplink transmitted by thePDCCH. The new data indicators are configured separately for eachtransport block to be transmitted. The user terminal UE can decidewhether or not to transmit new packets based on the new data indicatorsincluded in the PDCCH.

When the user terminal UE is connected with the first cell and thesecond cell and the total transmission power on the uplink exceeds theupper limit in the PO period, the user terminal UE applies power scalingto new uplink packets and reduces the uplink transmission power.

(5) The user terminal UE may be configured to apply power scaling toretransmission packets. By this means, power scaling is applied toretransmission packet more preferentially than new packets, so that itis possible to reduce the probability of retransmissions of new packets.

(6) It is also possible to combine one of methods (1) to (5) above, withthe power scaling methods A and B described earlier. For example, whenapplying power scaling to TAGs having large transmission power, the userterminal UE may apply power scaling on a per uplink physical channelbasis, in the order of priorities of: PRACH>PUCCH>PUSCH>SRS. Whenapplying power scaling to TAGs having large transmission power, the userterminal UE may apply power scaling by prioritizing Pcell over Scell.

Next, examples of the base station apparatus and the user terminal, towhich the radio communication method described above is applied, will bedescribed. Although a radio access system designed for LTE and LTE-Awill be described as an example, this by no means limits application toother systems.

FIG. 6 is a network configuration diagram of a mobile communicationsystem where a radio communication method according to an embodiment ofthe present invention is applied. The radio communication system 1 isconfigured to include base station apparatuses 20A and 20B, and aplurality of first and second mobile station apparatuses 10A and 10Bthat communicate with these base station apparatuses 20A and 20B. Thebase station apparatuses 20A and 20B are connected with a higher stationapparatus 30, and this higher station apparatus 30 is connected with acore network 40. The base station apparatuses 20A and 20B are connectedwith each other by wire connection or by wireless connection. The firstand second mobile station apparatuses 10A and 10B can communicate withthe base station apparatuses 20A and 20B in cells C1 and C2. The higherstation apparatus 30 may be, for example, an access gateway apparatus, aradio network controller (RNC), a mobility management entity (MME) andso on, but is by no means limited to these.

Although the first and second mobile station apparatuses 10A and 10B maybe both LTE terminals and LTE-A terminals, the following descriptionwill be given simply with respect to the “mobile station apparatus 10,”unless specified otherwise. Although, for ease of explanation, the firstand second mobile station apparatuses 10A and 10B will be described toperform radio communication with the base station apparatuses 20A and20B, more generally, it is also possible to use user equipment (UE),which may cover both mobile terminal apparatuses and fixed terminalapparatus.

In the radio communication system 1, as radio access schemes, OFDMA(Orthogonal Frequency Division Multiple Access) is adopted on thedownlink, and SC-FDMA (Single-Carrier-Frequency-Division MultipleAccess) is adopted on the uplink, but the uplink radio access scheme isnot limited to this. OFDMA is a multi-carrier transmission scheme toperform communication by dividing a frequency band into a plurality ofnarrow frequency bands (subcarriers) and mapping data to eachsubcarrier. SC-FDMA is a single carrier transmission scheme to reduceinterference between terminals by dividing, per terminal, the systemband into bands formed with one or continuous resource blocks, andallowing a plurality of terminals to use mutually different bands.

Now, communication channels in evolved UTRA and UTRAN will be described.On the downlink, a physical downlink shared channel (PDSCH), which isused by each mobile station apparatus 10 on a shared basis, and aphysical downlink control channel, which is a downlink control channel(PDCCH, or also referred to as a “downlink L1/L2 control channel”) areused. By the above physical downlink shared channel, user data—that is,normal data signals—is transmitted. Precoding information for uplinkMIMO transmission, information about the IDs of users that communicateusing the physical downlink shared channel and the users' data transportformats (that is, downlink scheduling information), and informationabout the IDs of users that communicate using the physical uplink sharedchannel and information about the users' data transport formats (thatis, uplink scheduling grants) and so on are fed back by means of thephysical downlink shared channel.

On the downlink, broadcast channels such as the P-BCH(Physical-Broadcast CHannel) and the D-BCH (Dynamic Broadcast CHannel)are transmitted. Information that is transmitted by means of the P-BCHincludes MIBs (Master Information Blocks), and information that istransmitted by means of the D-BCH includes SIBs (System InformationBlocks). The D-BCH is mapped to the PDSCH, and transmitted from the basestation apparatus 20 to the mobile station apparatuses 10.

As for the uplink, a physical uplink shared channel (PUSCH), which isused by each mobile station apparatus 10 on a shared basis, and aphysical uplink control channel (PUCCH), which is an uplink controlchannel, are used. By means of the physical uplink shared channel, userdata—that is, normal data signals—is transmitted. By means of thephysical uplink control channel, precoding information for downlink MIMOtransmission, delivery acknowledgment information for downlink sharedchannels, downlink radio quality information (CQI) and so on aretransmitted.

On the uplink, a physical random access channel (PRACH) for initialaccess and so on is defined. The mobile terminal apparatus 10 isdesigned to transmit random access preambles to the base stationapparatus 20 in the PRACH.

An overall configuration of a base station apparatus according to thepresent embodiment will be described with reference to FIG. 7. The basestation apparatuses 20A and 20B have the same configuration andtherefore will be described as the “base station apparatus 20.” Thefirst and second mobile station apparatuses 10A and 10B also have thesame configuration and therefore will be described as the “mobilestation apparatus 10.”

The base station apparatus 20 has a plurality of transmitting/receivingantenna 202 a, 202 b . . . for MIMO transmission, amplifying sections204 a, 204 b . . . , transmitting/receiving sections 206 a, 206 b . . ., a baseband signal processing section 208, a call processing section210, and a transmission path interface 212. The transmitting/receivingantennas 202 a and 202 b . . . are, for example, eight antennas, and theamplifying sections 204 a, 204 b . . . and the transmitting/receivingsections 206 a and 206 b . . . are provided in numbers to match thenumber of antennas.

User data that is transmitted from the base station apparatus 20 to themobile station apparatus 10 on the downlink is input from the higherstation apparatus 30 placed above the base station apparatus 20—forexample, the access gateway apparatus 30—into the baseband signalprocessing section 208, via the transmission path interface 212.

The baseband signal processing section 208 performs a PDCP layerprocess, division and coupling of user data, RLC (Radio Link Control)layer transmission processes such as an RLC retransmission controltransmission process, MAC (Medium Access Control) retransmissioncontrol, including, for example, an HARQ (Hybrid Automatic RepeatreQuest) transmission process, scheduling, transport format selection,channel coding, an inverse fast Fourier transform (IFFT) process, and aprecoding process, and transfers the result to thetransmitting/receiving sections 206 a and 206 b. The signal of thephysical downlink control channel is also subjected to transmissionprocesses such as channel coding and an inverse fast Fourier transform,and then transferred to the transmitting/receiving sections 206 a and206 b.

The baseband signal processing section 208 feeds back controlinformation for communication in the cell to the mobile stationapparatus 10, through the broadcast channels mentioned earlier. Thecontrol information for communication in the cell includes, for example,the uplink or downlink system bandwidth, resource block informationallocated to the mobile station apparatus 10, root sequenceidentification information (root sequence index) for generating randomaccess preamble signals in the PRACH and so on.

Baseband signals that are pre-coded and output from the baseband signalprocessing section 208 on a per antenna basis are subjected to afrequency conversion process and converted into a radio frequency bandin the transmitting/receiving sections 206 a and 206 b, and, after that,amplified in the amplifying sections 204 a and 204 b and transmittedfrom the transmitting/receiving antennas 202 a and 202 b.

As for data to be transmitted from the mobile terminal apparatus 10 tothe radio base station apparatus 20 on the uplink, radio frequencysignals that are received in the transmitting/receiving antennas 202 aand 202 b are amplified in the amplifying sections 204 a and 204 b,converted into baseband signals through frequency conversion in thetransmitting/receiving sections 206 a and 206 b, and input in thebaseband signal processing section 208.

The baseband signal processing section 208 applies, to the user dataincluded in the baseband signals received as input, an FFT process, anIDFT process, error correction decoding, a MAC retransmission controlreceiving process and RLC layer and PDCP layer receiving processes, andtransfers the result to the access gateway apparatus 30 via thetransmission path interface 212.

The call processing section 210 performs call processing such as settingup and releasing communication channels, manages the state of the basestation apparatus 20, and manages the radio resources.

A configuration of the baseband signal processing section 208 of theradio base station apparatus 20 according to the present embodiment willbe described with reference to FIG. 8. FIG. 8 is a functional blockdiagram of the baseband signal processing section 208 in the radio basestation apparatus 20 according to the present embodiment. In FIG. 8,configurations such as a scheduler 234 and others are also included forease of explanation.

Reference signals (quality measurement reference signals) included inreceived signals are input in a channel quality measurement section 221.The channel quality measurement section 221 measures uplink channelquality information (CQI) based on the received state of the referencesignals received from the mobile station apparatus 10. Received signalsthat are input in the baseband signal processing section 208 have thecyclic prefixes attached to the received signals removed in CP (CyclicPrefix) removing sections 222 a and 222 b, and, after that, convertedinto frequency domain information through a Fourier transform in fastFourier transform sections 224 a and 224 b. Symbol synchronizationsections 223 a and 223 b estimate the synchronization time from thereference signals included in the received signals, and report theestimation result to the CP removing sections 222 a and 222 b.

The received signals, converted into frequency domain information, aredemapped in the frequency domain in the subcarrier demapping sections225 a and 225 b. The subcarrier demapping sections 225 a and 225 bperform the demapping in accordance with the mapping in the mobilestation apparatus 10. Here, among the received signals received on theuplink, the received signal that is input in the subcarrier demappingsection 225 b is comprised of two uplink data codewords #2 and #3combined. The frequency domain equalization section 226 equalizes thereceived signals based on channel estimation values provided from achannel estimation section 227. The channel estimation section 227estimates channel states on a per component carrier basis from thereference signals included in the received signals, and the frequencydomain equalization section 226 equalizes the received signals(codewords) on a per component carrier basis.

The inverse discrete Fourier transform sections (IDFT) 228 a, 228 b and228 c apply an inverse discrete Fourier transform to the received signaland converts the frequency domain signals back to time domain signals.The data demodulation sections 229 a, 229 b and 229 c and the datadecoding sections 230 a, 230 b and 230 c reconstruct uplink user databased on the transport format of each component carrier (the codingrate, the modulation scheme and so on). By this means, the transmissiondata of codeword #1 corresponding to the first transport block, thetransmission data of codeword #2 corresponding to the second transportblock, and the transmission data of codeword #3 corresponding to thethird transport block are reconstructed.

The re-constructed transmission data of codewords #1, #2 and #3 isoutput to a retransmission information channel selection section 233.The retransmission information channel selection section 233 determineswhether or not it is necessary to retransmit the transmission data ofcodewords #1, #2 and #3 (ACK/NACK). Then, based on whether or not it isnecessary to retransmit the transmission data of codewords #1, #2 and#3, retransmission-related information such as NDI information and RVinformation is generated. The retransmission information channelselection section 231 selects the channel (the PHICH or the PDCCH (ULgrants)) to transmit the retransmission information.

The scheduler 234 determines uplink and downlink resource allocationinformation based on channel quality information (CQI) given from thechannel quality measurement section 221, and PMI information and RIinformation given from a precoding weight/rank selection section 235,which will be described later.

The precoding weight/rank selection section 235 determines precodingweights (PMIs) for controlling the phase and/or amplitude oftransmission signals on a per antenna basis in the mobile stationapparatus 10, from the uplink received quality in the resource blocksallocated to the mobile station apparatus 10, based on the channelquality information (CQI) given from the channel quality measurementsection 221. The precoding weight/rank selection section 235 determinesthe rank (RI), which represents the number of space multiplexing layersin the uplink, based on the channel quality information (CQI) given fromthe channel quality measurement section 221.

An MCS selection section 236 selects the modulation scheme/channelcoding rate (MCS) based on the channel quality information (CQI) givenfrom the channel quality measurement section 221.

A dedicated user data generating section 237 generates dedicateddownlink transmission data (dedicated user data) for each mobile stationapparatus 10, from user data that is input from the higher stationapparatus 30 such as the access gateway apparatus 30, in accordance withresource allocation information given from the scheduler 234.

With the present embodiment, the dedicated user data generating section237 functions as a control section that expressly indicates the TAG, towhich power scaling should be applied, to the mobile station apparatus10, based on control signals input from the higher station apparatus orinformation given from the scheduler 234, and signals power scalingtarget information such as the TAG to apply power scaling to, to themobile station apparatus 10. The target to apply power scaling to is notlimited to being provided in TAG units, but may also be provided incomponent carrier units, in uplink physical channel units, or in packetunits.

For example, it is possible to use the transmission quality and/or thetraffic of the connecting cells where the mobile station apparatus 10 isconnected, as a basis for decision making. The dedicated user datagenerating section 237 may expressly determine the TAG, to which powerscaling is applied in the mobile station apparatus 10, by using cellconfigurations as a basis for decision making. The dedicated user datagenerating section 237 may expressly determine the uplink physicalchannels to apply power scaling to, in physical channel units. Forexample, in the primary cell (TAG #1 and CC #1), the transmissionquality of the PRACH and the PUCCH may be prioritized over the PUSCH,and, in the secondary cell (TAG #2 and CC #2), the transmission qualityof the PUSCH and the SRS may be prioritized over the PUCCH. In thiscase, the base station apparatus 20 expressly determines the PUSCH ofTAG #1 (CC #1) as the target to apply power scaling to, and expresslydetermines the PUCCH of TAG #2 (CC #2) as the target to apply powerscaling to.

When cell C1 as the first cell is managed for control signals and cellC2 as the second cell is managed for data transmission, and thecomponent carriers included in the first cell C1 are classified as thefirst timing group and the component carriers included in the secondcell C2 are classified as the second timing group, the PUCCH of thefirst timing group, the PUSCH and/or the SRS of the second timing groupare expressly determined as physical channels to which power scaling isapplied.

The dedicated user data generating section 237 generates user data forreporting the TAG (or the cell, the CC, the uplink physical channel, thepacket, etc.), to which power scaling is applied to, expresslydetermined by one of the above-described methods, to the mobile stationapparatus 10 by higher layer signaling.

The UL grant information generating section 238 generates a DCI format,which includes the above-described UL grant, based on ACK/NACKinformation and retransmission-related information (NDI information andRV information) given from the retransmission information channelselection section 233, resource allocation information given from thescheduler 234, PMI and RI information given from precoding weight/rankselection section 233, and MCS information given from the MCS selectionsection 236.

The PHICH signal generating section 239 generates the PHICH signal,which includes a hybrid ARQ acknowledgement response for showing whetheror not a transport block needs to be retransmitted to the mobile stationapparatus 10, based on the ACK/NACK information andretransmission-related information (NDI information and RV information)given from the retransmission information channel selection section 233.

The PDSCH signal generating section 240 generates the downlinktransmission data to actually transmit by the physical downlink shardchannel (PDSCH), based on the downlink transmission data (dedicated userdata) generated in the dedicated user data generating section 237. ThePDCCH signal generating section 241 generates the PDCCH signal tomultiplex over the PDCCH based on the DCI format including the UL grant,generated in the UL grant information generating section 238.

The PHICH signal, the PDSCH signal and the PDCCH signal generated inthese PHICH signal generating section 239, PDSCH signal generatingsection 240 and PDCCH signal generating section 241 are input in an OFDMmodulation section 242. The OFDM modulation section 242 applies an OFDMmodulation process to two sequences of signals including these PHICHsignal, PDSCH signal and PDCCH signal, and transmits the results to thetransmitting/receiving sections 206 a and 206 b.

In this way, the base station apparatus 20 expressly indicates the TAG(or the CC, the uplink physical channel, the packet, etc.), to whichpower scaling is applied, to the mobile station apparatus 10, andsignals power scaling target information such as the TAG to apply powerscaling to, to the mobile station apparatus 10, by higher layersignaling. By this means, it becomes possible to determine the TAGand/or the like, to which the mobile station apparatus 10 should applypower scaling, in the base station apparatus 20, so that it is possibleto improve the flexibility in network management. The base stationapparatus 20 can flexibly determine the TAG (or the cell, the CC, theuplink physical channel, the packet, etc.), to which power scalingshould be applied, by taking into account the communication environment(the cell configurations, the conditions of carrier aggregation,transmission quality, traffic, transmission power, transport block size,packet type and so on), and reduce the deterioration of uplinktransmission quality due to application of power scaling. Since powerscaling target information is reported to the mobile station apparatus10 through higher layer signaling, it is also possible to reduce theoverhead.

Next, a configuration of a mobile station apparatus 10 according to thepresent embodiment will be described with reference to FIG. 9. As shownin FIG. 9, the mobile station apparatus 10 according to the presentembodiment has two transmitting/receiving antennas 102 a and 102 b forMIMO transmission, amplifying sections 104 a and 104 b,transmitting/receiving sections 106 a and 106 b, a baseband signalprocessing section 108, and an application section 110.

As for downlink data, radio frequency signals that are received in thetwo transmitting/receiving antennas 102 a and 102 b are amplified in theamplifying sections 104 a and 104 b, and converted into baseband signalsthrough frequency conversion in the transmitting/receiving sections 106a and 106 b. The baseband signals are subjected to an FFT process, errorcorrection decoding, a retransmission control receiving process and soon in the baseband signal processing section 108. In this downlink data,downlink user data is transferred to the application section 110. Theapplication section 110 performs processes related to higher layersabove the physical layer and the MAC layer. In the downlink data,broadcast information is also transferred to the application section110.

Uplink user data is input from the application section 110 to thebaseband signal processing section 108. The baseband signal processingsection 108 performs a retransmission control (H-ARQ: Hybrid ARQ)transmission process, channel coding, precoding, DFT process, IFFTprocess and so on, and transfers the result to thetransmitting/receiving sections 106 a and 106 b. The baseband signalsoutput from the baseband signal processing section 108 are subjected toa frequency conversion process and converted into a radio frequency bandin the transmitting/receiving sections 106 a and 106 b, and, after that,amplified in the amplifying sections 104 a and 104 b and transmittedfrom the transmitting/receiving antennas 102 a and 102 b.

FIG. 10 is a block diagram showing a configuration of the basebandsignal processing section 108. The baseband signal processing section108 is primarily formed with a layer 1 processing section 1081, a MACprocessing section 1082, an RLC processing section 1083, a transmissionpower setting section 1084, a TPC command received processing section1085 and a TPC command format receiving processing section 1086.

The layer 1 processing section 1081 mainly performs processes related tothe physical layer. The layer 1 processing section 1081, for example,applies processes such as channel decoding, a discrete Fouriertransform, frequency demapping, an inverse Fourier transform and datademodulation to signals received on the downlink. The layer 1 processingsection 1081 performs processes for signals to transmit on the downlink,including channel coding, data modulation, frequency mapping and aninverse fast Fourier transform (IFFT).

The MAC processing section 1082 performs, for the signals received onthe downlink, MAC layer retransmission control (hybrid ARQ), an analysisof downlink scheduling information (specifying the PDSCH transportformat and specifying the PDSCH resource blocks) and so on. The MACprocessing section 1082 performs, for the signals to transmit on theuplink, MAC retransmission control, an analysis of uplink schedulinginformation (specifying the PUSCH transport format and specifying thePUSCH resource blocks and so on) and so on.

The RLC processing section 1043 performs, for packets received on thedownlink/packets to transmit on the uplink, packet division, packetcombining, RLC layer retransmission control, and so on.

The TPC command receiving process section 1085 receives TPC commandsreported from the base station apparatus 20, and detects the contents ofthe TPC commands. The TPC command receiving process section 1085 detectsthe contents of the TPC commands based on TPC command formats receivedin the TPC command format receiving process section 1086. Informationabout the TPC commands is sent to the transmission power setting section1084.

The TPC command format receiving process section 1086 receives thesignals of TPC command formats reported from the radio base stationapparatus. The TPC command format receiving process section 1086receives a TPC command format signal with an expanded number of bits(for example, three bits) upon uplink MU-MIMO transmission. When uplinkMU-MIMO transmission is not carried out, the TPC command formatreceiving process section 1086 receives the TPC command format signalthat is defined in the LTE system. Information about the TPC commandformats is sent to the transmission power setting section 1084.

The transmission power setting section 1084 sets transmission powerusing transmission power control information (TPC command formats andTPC commands). To the mobile station apparatus 10, the TAG (or the cell,the CC, the uplink physical channel, the packet, etc.), to which powerscaling is applied, is reported from the base station apparatus 20 onthe downlink. If, in the state in which MTA is applied, the totaltransmission power exceeds the upper limit value defined, thetransmission power setting section 1084 applies power scaling to the TAG(the cell, the CC, the uplink physical channel or the packet) that isreported in advance, and reduces the transmission power.

For example, assume that the TAG to apply power scaling to is reportedas the target of power scaling in the state in which the mobile stationapparatus 10 is connected with multiple cells C1 and C2. In this case,if MTA is applied to the mobile station apparatus 10 and the totaltransmission power exceeds the upper limit in the PO period (see FIG.4), the transmission power setting section 1084 reduces the transmissionpower of the CCs included in the TAG reported in advance.

Assume that, in the state in which the mobile station apparatus 10 isreported to cell C1 that serves as the primary cell and to cell C2 thatserves as the secondary cell, for example, the primary cell is reportedas the cell to which power scaling is applied. In this case, if MTA isapplied to the mobile station apparatus 10 and the total transmissionpower exceeds the upper limit in the PO period, the transmission powersetting section 1084 reduce the transmission power of the primary cellthat is reported in advance.

The mobile station apparatus 10 may acquire information that linksphysical channels with cells, in advance, and have the cell where powerscaling is applied reported from the base station apparatus 20. Forexample, assume that, when the primary cell C1 for control signals (TAG#1 and CC #1) becomes the target of power scaling, the data signal(PUSCH) in the primary cell C1 is determined to be subject to powerscaling. When the total transmission power exceeds the upper limit inthe PO period, if the primary cell C1 (TAG #1 and CC #1) is reported inadvance as the target of power scaling, the mobile station apparatus 10reduces the transmission power of the PUSCH of the primary cell C1.Alternatively, assume that, when the secondary cell for datatransmission (TAG #2 and CC #2) becomes the target of power scaling, thecontrol signal (PUCCH) in the secondary cell is determined to be subjectto power scaling. When the total transmission power exceeds the upperlimit in the PO period, if the secondary cell (TAG #2 and CC #2) isreported in advance as the target of power scaling, the user terminal UEreduces the transmission power of the PUCCH of the secondary cell.

When the base station apparatus 20 expressly determines the PUSCH of TAG#1 (CC #1) as the target to apply power scaling to, and expresslydetermines the PUCCH of TAG #2 (CC #2) as the target to apply powerscaling to, the mobile station apparatus 10 has information about thesetargets of power scaling determined in this way reported from the basestation apparatus 20. In this case, in the mobile station apparatus 10,when the total transmission power in the PO period exceeds the upperlimit, the transmission power setting section 1084 reduces thetransmission power of the physical channels that are reported inadvance. For example, if the PUSCH of TAG #1 (CC #1) is determined to bethe target to apply power scaling to, the transmission power of thePUSCH of TAG #1 (CC #1) is reduced.

Alternatively, by implicitly determining the TAG, to which power scalingis applied, even when the above power scaling methods (1) to (5) tomaintain transmission quality are applied, without carrying outsignaling, the transmission power setting section 1084 reduces thetransmission power of the TAG (the cell, the CC, the uplink physicalchannel, or the packet) by applying one of the power scaling methods (1)to (5) described above, in the PO period in which the total transmissionpower exceeds the upper limit.

For example, when power scaling is determined to be applied to a TAGhaving large transmission power, the transmission power setting section1084 calculates the sum of transmission power per TAG, and applies powerscaling to the TAG of the largest transmission power. At this time,signaling of power scaling target information from the base stationapparatus 20 is not necessary.

When power scaling is determined to be applied to the PUSCH of a smalltransport block size (with a small number of transmission bits), forexample, if transport blocks are allocated to cell C1 and cell C2, thetransmission power setting section 1084 reduces the transmission powerof the cell where the transport block of the larger size is allocated.By this means, it is possible to reduce the overhead uponretransmissions. At this time, signaling of power scaling targetinformation from the base station apparatus 20 is not necessary.

When power scaling is determined to be applied to a TAG where the totalallocation bandwidth is small, if CC #1 alone is allocated to cell C1and CC #2 and CC #3 are allocated to cell C2, the transmission powersetting section 1084 applies power scaling to the TAG of cell C1.

When power scaling is determined to be applied to new uplink packets,the transmission power setting section 1084 applies power scaling to newpackets in accordance with detection results in the new datatransmission/retransmission determining section 115. When power scalingis determined to be applied to retransmission packets, the transmissionpower setting section 1084 applies power scaling to retransmissionpackets in accordance with detection results in the new datatransmission/retransmission determining section 115. Whether the targetpackets to apply power scaling to are new packets or retransmissionpackets on the uplink depends on system management.

The configuration of the layer 1 processing section 1081 in the basebandsignal processing section 108 of the mobile station apparatus 10 will bedescribed with reference to FIG. 11. A shown in this drawing, receivedsignals output from the transmitting/receiving sections 106 a and 106 bare demodulated in the OFDM demodulation section 111. Of the downlinkreceived signals demodulated in the OFDM demodulation section 111, thePDSCH signal is input in the downlink PDSCH decoding section 112, thePHICH signal is input in the downlink PHICH decoding section 113, andthe PDCCH signal is input in the downlink PDCCH decoding section 114.The downlink PDSCH decoding section 112 decodes the PDSCH signal, andreconstructs the PDSCH transmission data. The downlink PHICH decodingsection 113 decodes the downlink PHICH signal. The downlink PDCCHdecoding section 114 decodes the PDCCH signal. DCI format to include ULgrants is included in the PDCCH signal. When power scaling targetinformation is signaled from the base station apparatus 20 to the mobilestation apparatus 10 through higher layer signaling, the power scalingtarget information is included in the transmission data that is given bydecoding the PDSCH signal.

When a hybrid ARQ acknowledgment response (ACK/NACK) is included in thePHICH signal decoded in the downlink PHICH decoding section 113, the newdata transmission/retransmission determining section 115 decides betweena new data transmission or a retransmission based on this hybrid ARQacknowledgment response (ACK/NACK). When a hybrid ARQ acknowledgement(ACK/NACK) is included in the UL grant of the PDCCH signal, the new datatransmission/retransmission determining section 115 decides between anew data transmission or a retransmission based on this hybrid ARQacknowledgment response (ACK/NACK). The determined results are reportedto a new transmission data buffer section 116 and a retransmission databuffer section 117.

The new transmission data buffer section 116 buffers uplink transmissiondata input from the application section 110. The retransmission databuffer section 117 buffers transmission data output from the newtransmission data buffer section 116. When a determined result to theeffect of a new data transmission is reported from the data newtransmission/retransmission determining section 115, uplink transmissiondata is generated from the transmission data in the new transmissiondata buffer section 116. When a determined result to the effect of adata retransmission is reported from the data newtransmission/retransmission determining section 115, uplink transmissiondata is generated from the transmission data in the retransmission databuffer section 117.

The uplink transmission data that is generated is input in aserial-to-parallel conversion section, which is not illustrated. In thisserial-to-parallel conversion section, the uplink transmission data issubjected to serial-to-parallel conversion and converted into a numberof codewords to match the uplink rank. The codewords represent thecoding unit in channel coding, and the number thereof (the number ofcodewords) is determined uniquely from the rank and/or the number oftransmitting antennas. A case is shown here where the number ofcodewords is determined to be three. The number of codewords and thenumber of layers (rank) do not always become equal. Uplink codeword #1transmission data, uplink codeword #2 transmission data and uplinkcodeword #3 transmission data are input in the data coding sections 118a, 118 b and 118 c.

The data coding section 118 a encodes the uplink codeword #1transmission data. The uplink codeword #1 transmission data encoded inthe data coding section 118 a is modulated in the data modulationsection 119 a, and multiplexed in the multiplexing section 120 a, and,after that, time sequence information having been subjected to adiscrete Fourier transform in the discrete Fourier transform section(DFT) 121 a is converted into frequency domain information. The datacoding section 118 a and the data modulation section 119 a perform thecoding and modulation processes of the uplink codeword #1 transmissiondata based on MCS information from the downlink PDCCH decoding section114. The subcarrier mapping section 112 a performs frequency domainmapping based on scheduling information (resource allocationinformation) from the downlink PDCCH decoding section 114. In the datacoding sections 118 b and 118 c to the subcarrier mapping sections 122 band 122 c, the same processes are applied to uplink codewords #2 and #3as those applied to uplink codeword #1.

Then, with the uplink codeword #1 transmission data after the mapping,the transmission signals are subjected to an inverse fast Fouriertransform in the inverse fast Fourier transform sections (IFFT) 123 a,123 b and 123 c, and converted from frequency domain signals to timedomain signals. Then, in cyclic prefix (CP) attaching sections 124 a,124 b and 124 c, cyclic prefixes are attached to the transmissionsignals. Here, the cyclic prefixes function as guard intervals forcancelling multipath propagation delays and differences in the times ofreception between a plurality of users in the base station apparatus 20.

Assume that CC #1 is allocated to cell C1, two CC #2 and CC #3 areallocated to cell C2, CC #1 is classified as TAG #1, and CC #2 and CC #3are classified as TAG #2. Assume that MTA is applied to the mobilestation apparatus 10 that is connected to cell C1 and cell C2, TAG #1 isset at transmission time T1, and TAG #2 is set at transmission time T2.With the present embodiment, uplink data (codeword #1) is transmitted onthe uplink of cell C1, and uplink data (codewords #2 and #3) istransmitted on the uplink of cell C2.

Under the above circumstances, for the transmission signal (codeword #1)of the uplink data of cell C1, the transmission time is controlled totime T1 in the MTA processing section 125 a. For the transmission signal(codeword #2) of the uplink data of cell C2, the transmission time iscontrolled to time T2 in the MTA processing section 125 b, and, for thetransmission signal (codeword #3), the transmission time is controlledto time T2 in the MTA processing section 125 c. The transmission signal(codeword #2) and the transmission signal (codeword #3), which are theuplink data of cell C2, are both controlled to time T2, and furthermorecombined in a combiner 126.

In this way, the TAG and/or the like, to which the mobile stationapparatus 10 should apply power scaling, are expressly determined in thebase station apparatus 20 and signaled, so that the mobile stationapparatus 10 is able to apply power scaling to the power scaling targetthat is reported. As a result of this, it is possible to apply powerscaling to the power scaling target, which the base station apparatus 20determines taking into account the communication environment (cellconfigurations, the conditions of carrier aggregation, transmissionquality, traffic, transmission power, transport block size, packet typeand so on), so that it is possible to reduce the deterioration of uplinktransmission quality due to application of power scaling.

Although the present invention has been described in detail withreference to the above embodiment, it should be obvious to a personskilled in the art that the present invention is by no means limited tothe embodiment described herein. The present invention can beimplemented with various corrections and in various modifications,without departing from the spirit and scope of the present inventiondefined by the recitations of the claims. Consequently, the descriptionsherein are provided only for the purpose of explaining examples, andshould by no means be construed to limit the present invention in anyway.

The disclosure of Japanese Patent Application No. 2012-218198, filed onSep. 28, 2012, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

1. A radio communication system, in which multiple cells are formed, andwhich comprises a plurality of base station apparatuses that each form acell included in the multiple cells, and a user terminal that canconnect to at least a first cell and a second cell included in themultiple cells, wherein: the base station apparatuses comprises: acontrol section that controls uplink transmission times per timing groupincluding one component carrier or a plurality of component carriers;and a transmission section that signals a timing group or a componentcarrier determined as a target of power scaling, as power scaling targetinformation, in which the timing group or the component carrier, towhich power scaling is applied, is expressly determined, to the userterminal; and the user terminal comprises: a receiving section thatreceives the power scaling target information signaled from the basestation apparatus; a transmission section that transmits uplink signalsat different transmission times per timing group; and a power controlsection that, when a total of uplink signal transmission power over thefirst cell and the second cell exceeds a predetermined value, appliespower scaling to the timing group or the component carrier determined inthe power scaling target information.
 2. The radio communication systemaccording to claim 1, wherein the base station apparatus signals thetiming group or the component carrier determined as the target of powerscaling to the user terminal through higher layer signaling.
 3. Theradio communication system according to claim 1, wherein the basestation apparatus expressly determines the timing group or the componentcarrier, to which power scaling is applied, by using, as an indicator,at least one of transmission quality and traffic of the multiple cells,to which the user terminal is connected at the same time.
 4. The radiocommunication system according to claim 1, wherein: when componentcarriers included in each cell, to which the user terminal is connectedat the same time, are classified into a plurality of timing groups, thebase station apparatus expressly determines a specific physical uplinkchannel in each timing group as a physical channel, to which powerscaling is applied, and signals the target of power scaling per physicalchannel; and when the total of uplink signal transmission power overmultiple cells, to which the user terminal is connected at the sametime, exceeds the predetermined value, the user terminal applies powerscaling to the physical channels reported as the target of powerscaling.
 5. The radio communication system according to claim 1,wherein, when the user terminal is connected to the first cell and thesecond cell at the same time, the first cell is managed for controlsignals, the second cell is managed for data transmission, a componentcarrier included in the first cell is classified as a first timinggroup, and a component carrier included in the second cell is classifiedas a second timing group, the base station apparatus expresslydetermines a physical uplink control channel (PUCCH) of the first timinggroup, a physical uplink shared channel (PUSCH) of the second timinggroup, and/or a reference signal (SRS) for channel quality measurement,as physical channels, to which power scaling is applied.
 6. The radiocommunication system according to claim 1, wherein, when the total ofuplink signal transmission power over multiple cells, to which the userterminal is connected at the same time, exceeds the predetermined value,the user terminal allocates power to a specific physical uplink channelpreferentially, and, excluding the specific physical uplink channel,applies power scaling to the timing group or the component carrierdetermined as the target of power scaling.
 7. A base station apparatusthat forms a cell in a radio communication system where multiple cellsare formed, the base station apparatus comprising: a control sectionthat controls uplink transmission times per timing group including onecomponent carrier or a plurality of component carriers; and atransmission section that signals a timing group or a component carrierdetermined as a target of power scaling, as power scaling targetinformation, in which the timing group or the component carrier, towhich power scaling is applied, is expressly determined, to the a userterminal, wherein the user terminal is connected to multiple cells andcontrolled to different transmission times per timing group.
 8. A userterminal that connects to multiple cells in a radio communication systemwhere a plurality of base station apparatuses form multiple cells, theuser terminal comprising: a receiving section that receives powerscaling target information signaled from the base station apparatus; atransmission section that transmits uplink signals at differenttransmission times per timing group; and a power control section that,when a total of uplink signal transmission power over connecting cellsexceeds a predetermined value, applies power scaling to the timing groupor the component carrier determined in the power scaling targetinformation.
 9. A radio communication method in a radio communicationsystem where multiple cells are formed, wherein: the radio communicationsystem comprises a plurality of base station apparatuses that each forma cell included in the multiple cells, and a user terminal that canconnect to at least a first cell and a second cell included in themultiple cells; and the radio communication method comprises the stepsof: controlling uplink transmission times per timing group including onecomponent carrier or a plurality of component carriers; signaling atiming group or a component carrier determined as a target of powerscaling, as power scaling target information, in which the timing groupor the component carrier, to which power scaling is applied, isexpressly determined, to the user terminal; in the user terminal,receiving the power scaling target information signaled from the basestation apparatus; transmitting uplink signals at different transmissiontimes per timing group; and when a total of uplink signal transmissionpower over multiple cells, to which the user terminal is connected atthe same time, exceeds a predetermined value, applying power scaling tothe timing group or the component carrier determined in the powerscaling target information.